The present invention relates to the formation of filaments, tow, and nonwoven webs. More particularly, the present invention relates to the formation of filaments, tow, and nonwoven webs from a thermoplastic polymer by hydraulic spinning.
Traditional melt-extrusion process for the formation of fibers or filaments, tow, and nonwoven webs from a thermoplastic polymer typically involve melting the thermoplastic polymer, extruding the molten polymer through a plurality of orifices to form a plurality of threadlines or filaments, attenuating the filaments by mechanical drawing or by entrainment in a rapidly moving first stream of gas, cooling the filaments with a second stream of gas, and gathering the cooled filaments by randomly depending them on a moving foraminous surface. The most common and well known of these processes are spinning, melting blowing, coforming, and spunbonding.
Meltblowing references include, by way of example, U.S. Pat. Nos. 3,016,559 to Perry, Jr., 3,704,198 to Prentice, 3,755,527 to Keller et al., 3,849,241 to Butin et al. et al., 3,978,185 to Butin et al., and 4,663,220 to Wisneski et al. See, also, V. A. Wente, "Superfine Thermoplastic Fibers", Industrial and Engineering Chemistry, Vol. 48, No. 8, pp, 1342-1346 (1956); V. A. Wente et al., "Manufacture of Superfine Organic Fibers", Navy Research Laboratory, Washington, D.C., NRL Report 4364 (111437), dated May 25, 1954, United States Department of Commerce, Office of Technical Services; and Robert R. Butin and Dwight T. Lohkamp, "Melting Blowing--A One-Step Web Process for New Nonwoven Products", Journal of the Technical Association of the Pulp and Paper Industry, Vol. 56, No. 4, pp. 74-77 (1973).
Of interest with respect to melting blowing techniques is U.S. Pat. No. 3,959,421 to Web et al. The patent relates to a method for the rapid quenching of meltblown fibers. A liquid, such as water, is sprayed into the gas stream containing meltblown microfibers to rapidly cool the fibers and the gas. The quenching liquid preferably is sprayed into the gas stream from opposite sides, and the temperature of the gas stream preferably is substantially higher than the boiling point of the quenching liquid in the area where the liquid is sprayed into the gas stream.
Coforming references (i.e., references disclosing a meltblowing process in which fibers or particles are comingled with the meltblown fibers as they are formed) include U.S. Pat. Nos. 4,100,324 to Anderson et al. and 4,118,531 to Hauser.
Finally, spunbonding references include, among others, U.S. Pat. Nos. 3,341,394 to Kinney, 3,655,862 to Dorschner et al., 3,692,618 to Dorschner et al., 3,705,068 to Dobo et al., 3,802,817 to Matsuki et al., 3,853,651 to Porte, 4,064,605 to Akiyama et al., 4,091,140 to Harmon, 4,100,319 to Schwartz, 4,340,563 to Appel and Morman, 4,405,297 to Appel and Morman, 4,434,204 to Hartman et al., 4,627,811 to Greiser and Wagner, and 4,644,045 to Fowells.
The above cited process have in common the attenuation of the threadlines or filaments by entrainment in a rapidly moving gaseous stream. It now has been discovered, however, that unique fibers and nonwoven webs can be obtained through the use of a liquid stream to attenuate the extruded filaments, in place of a gaseous stream.